Scratch building

Scratch building is the process of building a scale model "from scratch", i.e. from raw materials, rather than building it from a commercial kit, kitbashing or buying it pre-assembled.

A scratch-built Warhammer 40,000 Land Raider in 1/18 scale utilizing paperboard and cardboard.
A 7cm long scratch-built model of 1/700 scale Japanese gunboat Fushimi (1939), built out of paper and copper wire.
A scratch-built 1:87 scale model of an old Vespa garage in Causeway Bay, Hong Kong 1950s, mainly built out of Foamcore and plastic card.
A scratch-built 1:150 model of Hong Kong's 'Tong Lau' tenement building.

Scratch building is easiest if original plans of the subject exist; however, many models have been built from photographs by measuring a known object in the photograph and extrapolating the rest of the dimensions. The necessary parts are then fashioned out of a suitable material, such as wood, plastic, plaster, clay, metal, polymer clay, or even paper, and then assembled. Some purists consider a model not to be truly scratchbuilt unless all of the parts were made from raw materials. However most modellers would consider a model including commercial detail parts as scratchbuilt. Scratchbuilding a new body onto an altered ready-to-run chassis is also acceptable.